Process for making waterproof-paper board



Nov. 13, 1928.

Filed May a, 1925' Patented Nov. 13, 192%,

EDMUND RACHE, OF ST. PAUL, MINNESOTA, ASSIGNOR TO WALDORF PAPER PRODUCTS COMPANY, OF ST. PAUL, MINNESOTA, A CORPORATION OF MINNESOTA.

EROCESS FOR MAKING WATERPROOF-PAPER BOARD.

Application filed May 8,

Attempts have been made to produce a satisfactory paper board of this character by ordinary mixing of a bitumen or bituminous emulsions with paper fibre. Products thereby obtained have been somewhat unsatisfactory because of lack of uniform and intimate contact between the paper fibres and the bitumen particles, and conditions to promote the mutual attraction between the paper fibre and the bitumen particles have not been considered.

The object of my invention is to produce paper stock having highly efficient moistureproof qualities and intimate and uniform dis tribution of the waterproofing agent on the particles of the paper pulp.

Paper pulp after it has been through the initial stages of paper making, namely, heating and jordaning, possesses an ele'ctronegative charge on the surface of its fibre. In my process, this charge must be changed to render the paper pulp fibre recipient to the waterproofing material, which is a bitumen in an emulsified state, because emulsified bitumen also carries an electronegative charge. In order that the pulp and emulsified bitumen may have opposite electrostatic charges, I condition the pulp by adding to it in the beater approximately .77; (by weight of dry stock) of a salt having a multi-valent positive ion, such as ferric chloride. 1 select this material because of its easy solubility in water and the reaction it will have with the pulp.

The presence of sizing in the stock tends to reduce the quantity of the salt required to reverse the surface charge on the fibre, and the hardening salts in the water tend to react with the ferric chloride, thus increasing the quan tity required to reverse the surface charge on the fibre. It is to be understood that the above stated proportions of pulp and salt having a multivalent, positiveion, are based upon use of so called chip stock, containing a small amount of sizing, and employing water in the pulp which is not excessively hard, viz, contains only about six grains of hardness. Such chip stock is commonly used in the manufacture of paper board for making boxes.

In the preparation of the board, I use the above described paper. pul fibre and a bitumen such as asphalt, whicli has been emulsified by the use of an agent such as cheap soap,

1925. Serial No. 28,836.

sodium oleate, sodium abietate, or sulfonated petroleum soap. The bitumen waterproofing material having been prepared and the pulp fibre conditioned, the two materials are brought into extremely close contact with each other for a fraction of a second, thereby.

distributing the asphalt emulsion particles uniformly upon the fibres of the pulp. The proportion of the ingredients is preferably 40 parts of emulsion. to 60 parts paper pulp by weight dry.

Suitable apparatus for uniformly distributin the asphaltic emulsion particles upon the bres of the pulp is shown in the accompanying drawings. In this apparatus, a vertical shaft 1 carries a conical rotor 2 on its lower end and is adapted to be driven by power applied to a pulley 3 fixed on said shaft near the upper end thereof. The pcriphery of the rotor 2 is smooth and arranged to revolve within a dish-shaped receptacle 4, which is supplied with the pulp and bitumen through a pipe 5 communicating with the base of said receptacle. By means of large nuts 6 on the upper end of the shaft 1, said shaft may be raised or lowered to adjust the spacing of the rotor 2 from a smooth coacting surface 13 on the receptacle 4. The space between the rotor 2 and stationary surface 13 may be adjusted so as to give a clearance of from one thousandth to fifty thousandths of an inch.

The conditioned paper pulp is fed through a pipe 7 to a relatively small receptacle 8 at one side of the rotor and a pipe 9 isarranged to simultaneously deliver the asphalt or bitumen emulsion to the receptacle 8. The pipe 5 communicates with the bottom of the receptacle 8, so as to withdraw the pulp and bitumen therefrom, under the suction produced by the rotor 2. i

In operation, the shaft 3 is driven at a high speed bya suitable belt applied to the pulley 3, so as to produce centrifugal force sufficient to draw the pulp and bitumen emulsion through the minute space between the periphery of the rotor 2 and the surface 13. WVith the rotor in operation, the pulp and bitumen emulsion is fed through the pipes 7 and 9, respectively, in the proportion stated above, and is quickly drawn down through the pipe 5, through the receptacle 4 and out at the top of said receptacle over the surface 13. At the top of the rotor 2, a chamber 10 is arranged to guide the intimately mixed pulp and bitumen to an outlet pipe 11. As will be readily understood, the pul and bitumen emulsion, in passing through t e restricted passage-way at the periphery of the rotor 2, at a high speed, is brought into intimate contact, and this results in an unusually uniform distribution of asphalt emulsion upon the fibres of the pulp.

As an alternate method of procedure, the asphalt may be emulsified simultaneously with its passage through the machine shown in the drawings. Thus, the emulsifying agent may be introduced through a pipe 12 simultaneously with the delivery of the asphalt through the pipe 9.

Whether the bitumen emulsion is prepared simultaneously with or prior to the bringing together with the pulp, it will be understood that the positively charged pulp readily attracts the negatively charged asphalt particles, so that the latter becomes surface concentrated in the form of a film about the fibres. This uniform concentration of the bitumen emulsion upon the surfaces of the fibres may be called adsorption of the emulsion particles upon the fibre. This film concentration on the fibre insures excellent water-proof and moisture-proof quality in theboard or paper. One of the many uses to which the paper stock of the invention is adapted is the manufacture of a moisture-proof board having a filler made of my improved stock, overlaid with surface sheets or layers of more or less pervious paper stock.

Having described my invention what I claim as new and desireto Patent is:

1. The process of making impervious paper stock which consists in preparing a quantity of bitumen emulsion in which the emulsoid particles carry an electro-negative charge,

preparing paper pulp carrying an electropositive charge on the fibres and then intimately mixing the so-prepared emulsion and pulp to uniformly distribute the bitumen upon the surfaces of the paper fibres.

2. The process of making impervious paper stock, which consists in first preparing separate quantities of paper pulp and bitumen emulsion by developing therein respectively opposite electro-static charges and then intimately mixing said bitumen and stock, whereprotect by Lettersby a surface concentration of the bitumen is applied to the particles of paper stock.

3. The process of preparing water-proof paper stock, which consists in first treating paper pulp with a salt having multi-valent, positive ion, such as ferric chloride, and then intimately mixing the thus prepared stock and a liquid bitumen emulsion by bringing them together in a restricted opening while in rapid motion.

4. The process of preparing water-proof paper stock, which consists in treating paper pulp with a salt containing multi-valent, positive ion, adding emulsified asphalt to said pulp and intimately mixing the thus prepared paper pulp and asphalt by bringing them together in a restricted passageway while in rapid motion.

5. The process of preparing impervious paper stock, which consists in first treating paper pulp with a trivalent salt, such as ferric chloride, to render the pulp electropositive and then intimately mixing said pulp with emulsified asphalt, whereby the particles of pulp are uniformly coated with a film of asphalt.

6. The process of preparing water-proof paper stock which consists in adding bitumen emulsion to paper pulp by forcing said stock and emulsion at a high velocity through an annular orifice of not more than .05 of an inch in width.

7. The process of preparing water-proof,

paper stock which consists in simultaneously forcing bitumen emulsion and paper pulp at a high velocity through an annular orifice, restricted by a rotor revolving in the orifice.

8. The process of preparing moisture-proof paper board which consists in simultaneously introducing into a'receptacle paper pulp, a water-proof hydro-carbon in liquid form, and

an emulsifying agent for said hydro-carbon,

then forcing said ingredients while in rapid motion through a restricted passage-way of notmore than .05 of an inchin width to thereby adsorb said hydro-carbon on the fibres of said pulp, and finally pressing and drying the stock so produced into sheet form.

-In testimony whereof, I have hereunto signed my name to this specification.

EDMUND BACHE. 

